Fix duplicate ID attributes

[atsansone]

Fix any and all duplicate ID attributes. These appear mostly on the sidenav. This violates WCAG F77.

Error: Duplicate id attribute value "sidenav-27" found on the web page.
htmlcs: WCAG2AA.Principle4.Guideline4_1.4_1_1.F77

Example:

<ul class="nav flex-column flex-nowrap collapse " id="sidenav-27"> <li class="nav-hea...</ul>

Location:
(selector "#sidenav-27")